Radiographic scanning agents suitable for use with gamma cameras, rectilinear scanners, and similar instruments have been prepared in different formulations for imaging of many human organs. Common radioisotopes used include 99m-technetium, 113m-indium, and 111-indium. These radionuclides are desirable for human use because they have low energy gamma radiation and short half lives.
Indium and technetium radioisotopes have been widely used in intravenous preparations for the radiographic imaging of body organs and systems. The following U.S. patents disclose typical radiographic compositions: U.S. Pat. No. 3,983,227, Tofe, diphosphonate dry mixture for admixture with technetium to produce bone scanning agent; U.S. Pat. No. 4,002,730, Hartman, technetium labelled anionic starch derivatives for lung imaging; U.S. Pat. No. 4,066,742, Garrett, technetium-sulfur colloid for imaging the reticuloendothelial system (RES); U.S. Pat. No. 4,070,493, Nadeau, stannousphytate colloid for labeling with technetium to image the RES; U.S. Pat. No. 4,016,249, Adler, techentium-stannous pyrophosphate bone imaging agent; U.S. Pat. No. 4,017,595, Subramanian, indium-organic phosphonate bone imaging agent; U.S. Pat. No. 4,022,877, Shubert, technetium-organotin complexes for imaging the kidneys; U.S. Pat. No. 4,024,233, Winchell, technetium macroaggregated serum albumin compositions for lung imaging; U.S. Pat. No. 4,048,296, Wolfangel, technetium-sulfur colloid for imaging the RES; U.S. Pat. No. 4,057,616, Wolfangel, technetium labeled metal hydroxide colloids for lung imaging; U.S. Pat. No. 3,981,980, Baker, technetium labeled pyridoxals for imaging the biliary tract; and U.S. Pat. No. 3,992,513, Pethau, technetium labeled phospholipids for imaging the lung and liver.
Several literature articles refer to the use of 99m-technetium labeled diethylenetriaminepentaacetic acid (DTPA) for oral administration in determining gastric emptying times in humans and dogs. Chaudhuri, et al., J. Nucl. Med., 14, 622 (1973); Chaudhuri, J. Nucl. Med., 15, 391 (1974); and Chaudhuri, et al., J. Nucl. Med., 15, 483 (1974). The radiolabeled compound was added to a meal and was determined to be non-adsorbable and non-absorbable in the stomach and homogeneously distributed in the meal. Only gastric emptying times were investigated.
Further investigations into the determination of gastrointestinal physiological characteristics have involved technetium labeled sulfur colloids. Mahmud, et al., J. Nucl. Med., 16, 547, (1975) describe a method for evaluating and detecting gastroesophageal reflux. A 99m-technetium sulfur colloid was introduced to the stomach using a nasogastric tube. Heading, et al., Gastroenterology, 71, 45 (1976) disclose a double isotope scanning method for the simultaneous study of gastric emptying times of liquid and solid meal components. 113m-indium--DTPA was used as marker for the liquid phase and small pieces of paper impregnated with 99m technetium labeled sulfur colloid and encased in plexiglass were used to mark the solid phase. The double isotope method was adequate for determining gastric emptying times. Thomas, et al., J. Nucl. Med., 18, 896, (1977) disclose the use of a double isotope method to detect the afferent loop syndrome in the small intestine after failure to obtain adequate X-ray scans using barium. Intravenous iodine-131 labeled rose bengal was used to image the liver, and oral 99m-technetium labeled sulfur colloid was used as a solid phase marker for the double isotope measurement of gastric emptying. Rezai-Zadeh, et al., J. Nucl. Med., 18, 635 (1977) disclose the use of oatmeal and milk 99m-technetium sulfur colloid labeled meals to measure gastric emptying times in normal subjects.
Another technique reported in the literature for measuring gastric emptying times used a 99m-technetium labeled polyamine polymer formed from polystyrene and triethylenetetramine; Theodorakis, et al., J. Nucl. Med., 16, 575 (1975).